Is CVE-2026-8927 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-8927 being exploited in the wild.

How severe is CVE-2026-8927?

Informational severity, published 3 July 2026.

Is there a fix for CVE-2026-8927?

A patch was published on 2026-06-24: Fixed in curl version 8.21.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-8927 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-8927?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-8927: curl libcurl authentication state leak in proxy handle reuse

CVE-2026-8927 · Severity: info · Published 2026-07-03

A vulnerability in the libcurl library, which is widely used by applications to transfer data over networks, could allow sensitive authentication information to be leaked. When an application reuses a connection handle to talk to different proxy servers, it may accidentally send the login credentials intended for the first proxy to the second one. This could allow a malicious proxy operator to impersonate the user or gain unauthorized access to other network resources.

Quick answers

Is CVE-2026-8927 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-8927 being exploited in the wild.
How severe is CVE-2026-8927?: Informational severity, published 3 July 2026.
Which products and versions are affected?: curl libcurl 7.12.0 to 8.20.0.
Is there a fix for CVE-2026-8927?: A patch was published on 2026-06-24: Fixed in curl version 8.21.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-8927 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-8927?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A flaw in libcurl's handle reuse logic occurs when sequential transfers are configured via environment variables. If an initial transfer uses Digest authentication with a specific proxy, libcurl fails to reset the authentication state before a subsequent transfer. If the second transfer is routed through a different proxy, the 'Proxy-Authorization' header containing the authenticated state for the first proxy is leaked to the second. This is classified as CWE-294 (Authentication Bypass by Capture-replay). The vulnerability affects libcurl but not the curl command-line tool. Users are advised to upgrade to version 8.21.0 or avoid handle reuse when switching proxies.

Affected products

curl libcurl 7.12.0 to 8.20.0

Timeline

2026-05-18: disclosed: Reported to the curl project via HackerOne
2026-06-24: patched: Fixed in curl version 8.21.0
2026-06-24: advisory: Project advisory published

References

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